Stroke is one of the leading causes of death and disabilities. Recent research has reported that commencing rehabilitative activities 4 days after ischemic injury in animals resulted in significantly greater motor function recovery and cortical structural reorganization compared to animals that began the rehabilitation program 14 and 30 days after the injury. However, it is difficult to commence motor function rehabilitation early in many stroke patients because performing physical therapy requires certain levels of voluntary movement of the patients, which may take weeks to return. The major goal of this project is to explore effects of strong-effort mental training of muscle contractions that begins shortly (early) after stroke (in which stroke patients are unable to move) on motor function recovery and functional reorganization of the brain. Previous research from the PI's laboratory have demonstrated substantial improvements in motor output and cortical signals following a mental training program in both young and aging populations. Aim 1 of the study is to compare clinical outcome (motor function recovery) of stroke patients who are engaged in mental motor actions early after stroke with patients whose therapy begins after return of voluntary movement. Aim 2 is to examine neural mechanisms underlying motor function recovery. Two groups of stroke patients with similar brain damage and motor disabilities will be trained: one with mental activation procedure that commences as soon as the patient could mentally work, and the other with conventional physical therapy that starts after some spontaneous recovery of motor function. Motor functions will be evaluated periodically during the course of the training. The mental practice of disabled limb is similar to the process of strong voluntary muscle actions of healthy muscles except that the motor command is blocked by stroke-damaged pathways. Multi-channel EEG and functional MRI brain mapping will be performed during each motor-function evaluation to determine neural mechanisms that mediate the recovery. It is hypothesized that stroke patients who begins mental practice early will recover faster and more completely than those who start therapy late, and this will be reflected by functional reorganization of the central nervous system (CNS). The study may lead to an effective therapy that can be administered early after stroke to facilitate CNS reorganization that promotes motor function recovery. Animal studies have indicated that commencement of physical therapy shortly after stroke onset resulted in greater motor function recovery and more meaningful brain reorganization compared to a program that began the therapy a number of days later. However, in human stroke patients, conventional physical therapy cannot begin until the patients gain certain levels of voluntary movements in the affected limbs, which may take weeks. This study explores the effects of a therapy that requires stroke patients to mentally move their affected limbs many times shortly after stroke onset. Mentally-performed movements can be administered at any time following stroke, as long as the patients are awake and cognitively capable to use their mind. Numerous studies have demonstrated that mental training of motor actions improves motor performance and facilitates the brain's ability to control the movements. It is expected that stroke patients treated by the early therapy of mental movements will recover faster and more completely than the patients who will be treated by conventional therapy that begins much later after stroke onset. The findings of the study will likely lead to improved patient care and quality of life in those who suffer a stroke.